10.1 Kirchoff's laws and circuits

What are kirchoffs laws?

• The current that enters a circuit is the same as the current that leaves it. The law of conservation of charge.

• Sum of the e.m.fs = the sum of p.ds

What is the use of closed loops?

It is a single possible path for the current

How is the current distributed in a series circuit?

There’s only one path for current so it's the same in every position.

Rate of flow of charge is the same at all points.

How is the e.m.f distributed in series loop?

It only has one closed loop so the e.m.f is shared between the components. If the circuit contains two components with the same resistance, the e.m.f is shared equally between them. If the components have different resistances the component eith the greater resistance will take a greater proportion of the e.m.f.

How is e.m.f distributed with more than one source of e.m.f?

Add the e.m.f from each source, before sharing it betweeb the components. The sources of e.m.f are connected with opposing polarities

How is current distributed in a parallel circuit?

Parallel circuits provide more than one possible path for the charges. How much charge flows through each path depends on the resistance of the path. The greater the resistance of the branch, the lower the current that passes through it.

Each parallel branch can be thought of as a different circuit.

How does Kirchoff's law relate to parallel circuits?

In a parallel circuit there are several different loops. Each branch forms is own loops. Kirchoff's second law tells us that around each loop the e.m.f must equal the p.d so the total p.d across each branch is equal to the e.m.f from the power supply. If one branch contains several components then the sum of the p.ds across these components must equal the e.m.f.

How does adding components affect e.m.f in series?

It reduces the e.m.f that is shared between the original components.